The present invention relates to heat exchangers and more particularly to a rotary heat exchanger for heat exchange between at least two gaseous media.
In one form of a rotary heat exchanger, as disclosed in German patent specification No. 1 551 457, the heat exchanger comprises an annular heat transfer member which is disposed rotatably in a housing of the apparatus. The heat transfer member may comprise a fibre material forming a three-dimensional lattice structure. Provided in the interior of the heat transfer member and subdividing same into two semicircular chambers is a stationary partitioning wall. The housing of the heat exchanger has two inlet ports or openings which respectively communicate with the semicircular chambers defined in the interior of the heat transfer member. The heat exchanger further has two outlet diffuser chambers which are disposed in mutually opposite relationship, outside the heat transfer member, with the width of each outlet chamber increasing from its point at which it defines a narrow gap with the heat transfer member, towards the actual outlet of the respective outlet chamber. That heat exchanger is used in particular for heat exchange purposes between a feed air flow and an exhaust or outlet air flow in buildings in order to make energy savings by the recovery of heat from the exhaust air flow. The rotary heat transfer member also acts at the same time as a radial flow fan or blower both for the feed air flow and for the exhaust air flow, so that in most cases it is possible to eliminate additional fans for generating the appropriate air flows. The material used for the heat transfer member, besides fibre material, is generally open-pore foam material, in an annular form.
It is found that the degree of separation between the two flows of air, or other gaseous media in a heat exchange relationship, as well as the degree of efficiency of the above-indicated heat exchanger are good, in other words, there is only a slight degree of mixing as between the feed air and the exhaust air, of for example around 15%, and the temperature difference between the two flows, after passing through the heat exchanger, is only a few degrees Centigrade. However, there is a desire further to improve the values which have been achieved hitherto in those respects, in the interests of maximising energy saving and minimising mixing of the two flows involved.